Many of today’s popular controller boards ship with a bootloader capable of updating firmware via SD Card. While this is convenient in many circumstances, these bootloaders typically provide no other way to update firmware. This can be a nuisance if your board is mounted in a location that is difficult to access or if you need to update firmware often. After Klipper has been initially flashed to a controller it is possible to transfer new firmware to the SD Card and initiate the flashing procedure via ssh.

Typical Upgrade Procedure

The procedure for updating MCU firmware using the SD Card is similar to that of other methods. Instead of using make flash it is necessary to run a helper script, flash-sdcard.sh. Updating a BigTreeTech SKR 1.3 might look like the following:

sudo service klipper stop
cd ~/klipper
git pull
make clean
make menuconfig
make
./scripts/flash-sdcard.sh /dev/ttyACM0 btt-skr-v1.3
sudo service klipper start

It is up to the user to determine the device location and board name. If a user needs to flash multiple boards, flash-sdcard.sh (or make flash if appropriate) should be run for each board prior to restarting the Klipper service.

Supported boards can be listed with the following command:

./scripts/flash-sdcard.sh -l

If you do not see your board listed it may be necessary to add a new board definition as described below.

Advanced Usage

The above commands assume that your MCU connects at the default baud rate of 250000 and the firmware is located at ~/klipper/out/klipper.bin. The flash-sdcard.sh script provides options for changing these defaults. All options can be viewed by the help screen:

./scripts/flash-sdcard.sh -h
SD Card upload utility for Klipper

usage: flash_sdcard.sh [-h] [-l] [-b <baud>] [-f <firmware>]
                       <device> <board>

positional arguments:
  <device>        device serial port
  <board>         board type

optional arguments:
  -h              show this message
  -l              list available boards
  -b <baud>       serial baud rate (default is 250000)
  -f <firmware>   path to klipper.bin

If your board is flashed with firmware that connects at a custom baud rate it is possible to upgrade by specifying the -b option:

./scripts/flash-sdcard.sh -b 115200 /dev/ttyAMA0 btt-skr-v1.3

If you wish to flash a build of Klipper located somewhere other than the default location it can be done by specifying the -f option:

./scripts/flash-sdcard.sh -f ~/downloads/klipper.bin /dev/ttyAMA0 btt-skr-v1.3

Note that when upgrading a MKS Robin E3 it is not necessary to manually run update_mks_robin.py and supply the resulting binary to flash-sdcard.sh. This procedure is automated during the upload process.

Caveats

  • As mentioned in the introduction, this method only works for upgrading firmware. The initial flashing procedure must be done manually per the instructions that apply to your controller board.
  • While it is possible to flash a build that changes the Serial Baud or connection interface (ie: from USB to UART), verification will always fail as the script will be unable to reconnect to the MCU to verify the current version.
  • Only boards that use SPI for SD Card communication are supported. Boards that use SDIO, such as the Flymaker Flyboard and MKS Robin Nano V1/V2, will not work.

Board Definitions

Most common boards should be available, however it is possible to add a new board definition if necessary. Board definitions are located in ~/klipper/scripts/spi_flash/board_defs.py. The definitions are stored in dictionary, for example:

BOARD_DEFS = {
    'generic-lpc1768': {
        'mcu': "lpc1768",
        'spi_bus': "ssp1",
        "cs_pin": "P0.6"
    },
    ...<further definitions>
}

The following fields may be specified:

  • mcu: The mcu type. This can be retrevied after configuring the build via make menuconfig by running cat .config | grep CONFIG_MCU. This field is required.
  • spi_bus: The SPI bus connected to the SD Card. This should be retreived from the board’s schematic. This field is required.
  • cs_pin: The Chip Select Pin connected to the SD Card. This should be retreived from the board schematic. This field is required.
  • firmware_path: The path on the SD Card where firmware should be transferred. The default is firmware.bin.
  • current_firmware_path The path on the SD Card where the renamed firmware file is located after a successful flash. The default is firmware.cur.

If software SPI is required the spi_bus field should be set to swspi and the following additional field should be specified:

  • spi_pins: This should be 3 comma separated pins that are connected to the SD Card in the format of miso,mosi,sclk.

It should be exceedingly rare that Software SPI is necessary, typically only boards with design errors will require it. The btt-skr-pro board definition provides an example.

Prior to creating a new board definition one should check to see if an existing board definition meets the criteria necessary for the new board. If this is the case, a BOARD_ALIAS may be specified. For example, the following alias may be added to specify my-new-board as an alias for generic-lpc1768:

BOARD_ALIASES = {
    ...<previous aliases>,
    'my-new-board': BOARD_DEFS['generic-lpc1768'],
}

If you need a new board definition and you are uncomfortable with the procedure outlined above it is recommended that you request one in the Klipper Community Discord.